Lumbar muscle function is considered to be an important component of chronic lower back pain (LBP). It has been found that individuals with endurable back muscles and general physical fitness have fewer incidences of back problems than deconditioned cohorts. Complementary studies have documented compromised muscle function in patients with LBP. Although the mechanism associating muscle insufficiency to LBP is not clearly understood, it is commonly held that the passive tissues of the spine are increasingly stressed with increasing functional muscle insufficiency. The high incidence of back injury among workers exposed to fatiguing manual tasks and whole body vibration lend support to this concept. To further understand the relationship of muscle function to LBP, more effective assessment procedures need to be developed and tested for clinical use.
Most techniques presently available to assess muscle deficiencies are either nonobjective or they lack rigorous clinical validation and reliability. One technique that does provide objective data entails electromyographic (EMG) spectral analysis of lower back muscles. Although providing advantages over other techniques, prior EMG systems have suffered certain deficiencies resulting primarily from treatment of individual muscle groups as a continuous muscle mass and exclusive reliance on the amplitude of EMG signals. Improved but less than fully satisfactory techniques utilizing EMG spectral measurements are disclosed in Merletti R., Biey D., Prato G., Orusa A.: On-line monitoring of the median frequency of the surface EMG power spectrum. IEEE Trans Biomed Eng BME-32 (no. 1): 1-7, 1985. Prior disclosures of EMG spectral analysis of LBP include Roy, S. H., DeLuca, C. J., Gilmore, L. D.: Computer Aided Back Analysis System. IEEE Engineering in Medicine and Biology Society-10th Annual International.
The object of this invention, therefore, is to provide an improved system for analyzing muscle fatigue associated with LBP.